I suggest all the metadata hooks use that order (object_id, key, value, meta_id).

That suggestion is a bad one.

The actions need to have arguments in the following order instead.

meta_id(s), object_id, key, value

I didn't realize that in addition to the (added|updated|update|deleted)_{$meta_type}_meta actions, there were already pre-existing (added|updated|update|deleted)_(post|user)_meta actions. These pre-existing actions all use the above argument order.

New patch puts them in the correct order.

Bumping severity since it's now a real bug, not just a new inconsistency.